This is a simple Python script that generates a presigned url for an object in S3.

• Python 3.6 or higher

• AWS credentials with access to S3

  • If you don't have AWS credentials, you can create a free account here.
  • Configure AWS credentials with aws configure command. You can find more information here.

Before you use this, make sure to understand the difference between

• GET, PUT request to the generated presigned url to S3. This will retrieve/upload the object to S3 from the presigned url straight without any additional steps.
• POST request with form data to the presigned url to S3. This will upload the object to S3, but you'll have to do additional steps by forming a proper form data and sending it to the presigned url.

1. Create virtual environment: python3 -m venv env
2. Activate virtual environment: source env/bin/activate
3. Install requirements: pip install -r requirements.txt. Optionally, you can check the installed packages with pip list
4. Generate the presigned url: python get_presigned_url.py
5. Use the presigned URL to retrieve/upload a file to S3. GET/PUT request methods.

Outputs a presigned url. Example: https://mybucketname.s3.amazonaws.com/uploads/path-to-file/file-name?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AAAAAAAAAA123456%2F20230222%2Fus-west-1%2Fs3%2Faws4_request&X-Amz-Date=20230222T075718Z&X-Amz-Expires=120&X-Amz-SignedHeaders=host&X-Amz-Signature=02b60ec8eb2af625648dd10a4400d1ea01495a95ab403a186a200fe34ffe1a63

1. Create virtual environment: python3 -m venv env
2. Activate virtual environment: source env/bin/activate
3. Install requirements: pip install -r requirements.txt. Optionally, you can check the installed packages with pip list
4. Generate the presigned url: python get_presigned_post.py
5. Use the key-value pairs defined in the output to create form data fields
6. Make POST request to the url in the output with the form data fields

Outputs a JSON data with url and fields.

• url: Presigned url endpoint
• fields: Form data fields that you need to send to the presigned url endpoint. Example:

  {
    "url": "https://bucketname.s3.amazonaws.com/",
    "fields": {
        "Content-Type": "image/*", // only images
        "key": "uploads/content/user-image.png",
        "x-amz-algorithm": "AWS4-HMAC-SHA256",
        "x-amz-credential": "AAAA1AAAAAAA11AAAA6/20230222/us-west-1/s3/aws4_request",
        "x-amz-date": "20230222T073320Z",
        "policy": "eyJleHBpcmF0aW9uIjogIjIwMjMtMDItMjJUMDc6MzU6MjBaIiwgImNvbmRpdGlvbnMiOiBbWyJjb250ZW50LWxlbmd0aC1yYW5nZSIsIDAsIDIwOTcxNTJdLCB7IkNvbnRlbnQtVHlwZSI6ICJpbWFnZS8qIn0sIHsiYnVja2V0IjogImVhemVsLWlvIn0sIHsia2V5IjogInVwbG9hZHMvdXNlcl9nZW5lcmF0ZWRfY29udGVudC91c2VyLWltYWdlLnBuZyJ9LCB7IngtYW16LWFsZ29yaXRobSI6ICJBV1M0LUhNQUMtU0hBMjU2In0sIHsieC1hbXotY3JlZGVudGlhbCI6ICJBS0lBNUlSTVRYTFJDNzRBQU1FNi8yMDIzMDIyMi9hcC1ub3J0aGVhc3QtMi9zMy9hd3M0X3JlcXVlc3QifSwgeyJ4LWFtei1kYXRlIjogIjIwMjMwMjIyVDA3MzMyMFoifV19",
        "x-amz-signature": "f486dcc93fe1a22707e4b27a0814d49adb366842597008980cb8895969ad304e"
    }
  }
  

  For more information on data in fields check HTML Form Fields

• get_presigned_url.py ->get_presigned_url(get_presigned_url(bucket_name, object_name, expiration=120)

  • bucket_name: Name of the bucket where the object is stored in S3. You should replace this with your bucket name.
  • object_name: Name of the object you want to access/upload/update/etc. You should replace this with your object name.
    • Note that / will create a folder in the bucket that you provide
    • For example: object_name = "folder1/folder2/folder3/file.txt" will create a folder structure like this: folder1 > folder2 > folder3 > file.txt
  • expiration: Expiration time of the presigned url in seconds. Default is 120 seconds.

• get_presigned_post.py -> get_presigned_post(get_presigned_url(bucket_name, object_name, expiration=120)

  • bucket_name: Name of the bucket where the object is stored in S3. You should replace this with your bucket name.
  • object_name: Name of the object you want to access/upload/update/etc. You should replace this with your object name.
    • Note that / will create a folder in the bucket that you provide
    • For example: object_name = "folder1/folder2/folder3/file.txt" will create a folder structure like this: folder1 > folder2 > folder3 > file.txt
  • expiration: Expiration time of the presigned url in seconds. Default is 120 seconds.

If you want to use this script in AWS Lambda, after configuring your Lambda function, depending on your needs copy the get_presigned_url() or get_presigned_post() into your lambda function.